Ideal body weight-based remifentanil infusion is potentially insufficient for anesthetic induction in mildly obese patients

We evaluated whether the effect of remifentanil treatment differs between normal weight (NW) patients with real body weight-based remifentanil and mildly obese (Ob) patients with ideal body weight based-remifentanil during short-term anesthetic induction. We enrolled 20 patients aged between 20 and 64 years in each group (NW group: 18.5 kg/m² ≤ BMI < 25 kg/m²; Ob group: BMI ≥ 25 kg/m²). Tracheal intubation (TI) was performed after administration of 0.5 μg/kg/min remifentanil for 5 min, including 2 min of antecedent administration, with propofol and rocuronium. Hemodynamic parameters (SBP, DBP, and HR) were measured. Percent changes in hemodynamics resulting from anesthetic induction and TI were calculated, and effect-site concentration (ESC) in each patient was calculated by performing pharmacokinetic simulation. All hemodynamic values in the Ob group after TI were significantly higher than those in the NW group. Percent increases in SBP and HR in the Ob group were significantly higher than the corresponding values in the NW group. ESC of remifentanil at the time of TI in the NW group was higher than that in the Ob group. Remifentanil treatment with anesthetic induction based on the Japanese package insert might have insufficient effects in obese patients.